Direct amplifying station and positioning method for mobile station thereof

ABSTRACT

“The present invention relates to a repeater for positioning mobile station and a method thereof. The repeater according to the present invention is implemented through adding a cell identifier generator module to the downlink circuit structure of a conventional repeater; said cell identifier generator module includes: a synchronization searching unit designed to search for base station synchronization signal, a time delay unit designed to generate a fixed delay between start time of cell identifier signal frame and start time of base station pilot signal frame, and a cell identifier signal generating unit designed to generate cell identifier signal code word. The mobile station positioning method determines the mobile station is in the coverage of the repeater on the basis that the time difference between base station pilot signal and cell identifier signal is consistent to the fixed delay; then the method utilizes TOA (Time of Arrival) measuring function to determine the distance from the mobile station to the repeater; thus it improves positioning accuracy of mobile stations in the coverage of the repeater. The repeater for positioning mobile station is easy to implement and can meet the positioning requirement of a plurality of mobile stations in the coverage of the repeater.”

FIELD OF THE INVENTION

The present invention relates to mobile communication field,particularly to a repeater for positioning mobile station and a methodthereof.

BACKGROUND OF THE INVENTION

To enable cellular mobile communication networks to provide newservices, such as E911 alarm, target tracking, position-basedinformation service (e.g., searching for the optimal traffic route orthe nearest petrol station), mobile station positioning technology hasto be introduced to position mobile stations.

Presently, there are 3 basic methods for positioning mobile stations incellular mobile communication networks: 1) TOA (Time Of Arrival)positioning method, which obtains distances from mobile station tocorresponding bases station through measuring TOAs of a mobile stationto three or more base stations and then estimates the position of themobile station through solving a circle equation set; 2) TDOA (TimeDifference Of Arrival) positioning method, which obtains distancedifference to corresponding base stations through measuring TDOAs from amobile station to three or more base stations and then estimates theposition of the mobile station through solving a hyperbolic equationset; 3) a method combining CELL-ID (Cell Identifier) and TOA, whichutilizes the cell identifier to determine the position of the servicecell where the mobile station is in and then further determine theposition of the mobile station in the cell through measuring TOA fromthe mobile station to the service base station.

In conventional mobile communication systems, to ensure normalcommunication between mobile stations and a base station, repeaters aredeployed in some areas that are not covered by the base station. FIG. 1is a structural diagram of a conventional RF repeater; in the downlinkdirection, the donating antenna (antenna of the service base station)picks up signals from an existing coverage area, filters off out-of-bandsignals with a band pass filter, and then retransmits the filteredsignals to an area to be covered via a power amplifier; in uplinkdirection, the signals from a mobile station in the coverage area areprocessed similarly and then transmitted to the corresponding basestation to implement signal transmission between the base station andthe mobile station. The introduction of a repeater implements normalcommunication between mobile stations and base station in the coverageof the repeater.

However, the introduction of repeater makes mobile stations in thecoverage of the repeater can't be positioned effectively. When a mobilestation to be positioned is in the coverage of the repeater, TDOApositioning process will fail because the number of detected basestations is too small; even though there are enough detected basestations, what is determined finally is the position of the repeater,the position of the mobile station in the coverage of the repeater can'tbe determined; furthermore, the positioning system is unable todetermine whether the positioning result has been affected by therepeater. Similarly, when a mobile station to be positioned is in thecoverage of the repeater, due to the effect of time delay in repeater RFchannel, the ‘TOA+CELL-ID’ method will result in severe TOA error, thusthe mobile station can't be positioned effectively.

To ensure effective positioning of mobile stations in the coverage ofthe repeater, a ‘repeater+auxiliary PE (Positioning Element)’ method canbe used in network deployment. However, the disadvantage of the methodis: to achieve effective positioning of mobile stations, at least 3 PEshave to be deployed in the coverage of each repeater, which increasescomplexity of network planning as well as device procurement expense andoperation and maintenance costs.

SUMMARY OF THE INVENTION

An object of the invention is to provide a repeater for positioningmobile station and a method thereof, in order to improve positioningaccuracy of mobile stations in the coverage of the repeater.

A repeater according to the present invention is implemented as follows:add a cell identifier generator module to downlink circuit structure ofthe repeater, said cell identifier generator module comprises: asynchronization searching unit for searching for synchronization signalof base station, a time delay unit for generating fixed delay betweenframe start time of cell identifier signal and frame start time of basestation pilot signal, and a cell identifier signal generating unit forgenerating cell identifier signal code word; said time delay unitgenerates the fixed delay according to the searching result of thesynchronization searching unit.

The input end of said cell identifier generator module is connected tothe low-noise amplifier module of the repeater; the output end of saidcell identifier generator module is connected to the power amplifiermodule of the repeater via a coupler.

Said cell identifier generator module also comprises: a down-conversionunit, an A/D (Analog to Digital) conversion unit, a D/A (Digital toAnalog) conversion unit, a up-conversion unit, and a filtering unit;wherein said down-conversion unit is designed to carry out frequencyconversion from RF to intermediate frequency for received signals; saidA/D conversion unit is designed to carry out sampling and quantificationfor intermediate frequency signals; said D/A conversion unit is designedto carry out D/A conversion to obtain base-band form of the cellidentifier signal; said up-conversion unit is designed to carry outconversion from base-band to RF for the cell identifier signal; saidfiltering unit is designed to carry out band restriction for the cellidentifier signal to control frequency leakage to adjacent frequency;said cell identifier signal is coupled to input end of power amplifierin the downlink circuit structure of the repeater via said D/A unit,up-conversion unit, and filtering unit.

The method for positioning mobile station according to the presentinvention is implemented as follows:

-   -   (1) Issuing cell identifier signal code word, fixed delay, and        search window width for the mobile station according to the        positioning request of the mobile station;    -   (2) The mobile station utilizing TDOA measuring function to        measure TDOAs of cell identifier signal and base station pilot        signal and reporting the measured data;    -   (3) Determining whether there is a time difference consistent to        the fixed delay between cell identifier signal and base station        pilot signal according to the reported data from the mobile        station; if so, going to step (4); otherwise going to step (7);    -   (4) Reading calibrated value TOA_(c) of TOA between the repeater        and the base station, and initiating RIT (Round Trip Time)        measuring function of the base station to measure RIT of the        mobile station, herein TOA_(c)=(½) RIT;    -   (5) Converting the measured RIT reported from the base station        into measured value TOA_(m) of TOA, herein TOA_(m)=(½) RIT,        which is the TOA from the mobile station to the base station via        the repeater, subtracting the calibrated value TOA_(c) of TOA        from the repeater to the base station from TOA_(m) and taking        the result as TOA TOA_(trans) from the mobile station to the        repeater, herein TOA_(trans)=TOA_(m)−TOA_(c);    -   (6) Calculating the distance between the mobile station and the        repeater through multiplying TOA_(trans) with light velocity;    -   (7) Determining position of the mobile station with the mobile        station positioning method.

Said cell identifier signal is a scrambling code of the base station,which is different from that of the adjacent base station.

Said mobile station positioning method in step (7) is TDOA positioningmethod.

Said mobile station positioning method in step (7) is TOA positioningmethod.

It is seen from above technical proposal that the repeater according tothe present invention delivers cell identifier signal transmittingfunction, which helps to determine whether the mobile station is in thecoverage of the repeater; the bandwidth of said cell identifier signalis identical to that of base station signals forwarded by the repeater;the code word of said cell identifier signal is chosen from thescrambling code set but is different from the scrambling code used bythe adjacent base station; said cell identifier signal keeps a fixedtime delay to pilot signal of the base station. The repeater for mobilestation positioning according to the present invention is easy toimplement and can meet the positioning requirement of a plurality ofmobile stations in the coverage of the repeater. The method for mobilestation positioning according to the present invention utilizes the cellidentifier signal of the base station transmitted by above repeater(with cell identifier signal transmitting function) and calibration fortime delay of the repeater to determine whether the mobile station is inthe coverage of the repeater; if so, said method utilizes TOA measuringfunction to further determine the distance from the mobile station tothe repeater; therefore, the method improves positioning accuracy ofmobile stations in the coverage of the repeater; if the mobile stationis not in the coverage of the repeater, the positioning is carried outwith an existing mobile station positioning method. Therefore, thepresent invention attains the object of improving positioning accuracyof mobile stations in the coverage of the repeater.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the diagram of a conventional repeater;

FIG. 2 shows the diagram of a repeater with cell identifier signaltransmitting function;

FIG. 3 is a schematic diagram of the timing relationship between cellidentifier signal frame and service base station frame;

FIG. 4 is a schematic diagram of an application that utilizes a repeaterto position mobile stations;

FIG. 5 is a flowchart of the mobile station positioning method accordingto the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To solve the problem that the mobile stations can't be positionedaccurately with conventional technologies, the present inventionprovides the technical solution for a repeater that supports mobilestation positioning and the technical solution for a method thatutilizes above repeater to position mobile stations.

As shown in FIG. 2, the repeater that supports mobile stationpositioning according to the present invention is implemented asfollows: a cell identifier generator module is added in the downlinkcircuit structure of a conventional repeater; the input end of said cellidentifier generator module is connected to the low noise amplifiermodule of the repeater, and the output end of said cell identifiergenerator module is connected to the power amplifier module of therepeater via a coupler.

Said cell identifier generator module comprises: a down-conversion unit,an A/D conversion unit, a synchronization searching unit, a time delayunit, a cell identifier signal generating unit, a D/A conversion unit, aup-conversion unit, and a filtering unit, wherein:

The down-conversion unit is designed to carry out frequency conversionfrom RF to intermediate frequency for received signals;

The A/D conversion unit is designed to carry out sampling andquantification for intermediate frequency signals;

The synchronization searching unit is designed to carry out framesynchronization to base station pilot signal in 3 steps: firstly, timeslot synchronization, secondly, frame synchronization, thirdly, mainscrambling code capturing;

The time delay unit is designed to generate fixed delay Td between framestart time of cell identifier signal and frame start time of basestation pilot signal;

The cell identifier signal generating unit is designed to generate cellidentifier signal code word;

The D/A conversion unit is designed to carry out D/A conversion toobtain base-band form of the cell identifier signal;

The up-conversion unit is designed to carry out conversion frombase-band to RF for the cell identifier signal;

The filtering unit is designed to carry out band restriction for thecell identifier signal to control frequency leakage to adjacentfrequency;

The time delay unit generates the fixed delay Td according to thesearching result of the synchronization searching unit;

The cell identifier signal code generated by the cell identifier signalgenerating unit is coupled to input end of the power amplifier in thedownlink circuit structure of the repeater via the D/A conversion unit,up-conversion unit, and filtering unit and then transmitted to thecoverage of the repeater along with base station signals forwarded bythe repeater, i.e., the cell identifier generator module can generateand transmit the cell identifier signal according to the fixed timedifference Td and a specific code word.

The mobile station positioning method based on a repeater that supportsmobile station positioning is further described as follows, withreference to FIG. 5 and FIG. 6:

Step 1: Issue cell identifier signal code, fixed delay Td and searchwindow width W for the mobile station according to the positioningrequest of the mobile station;

Wherein the cell identifier signal code comprises a scrambling codedifferent from the adjacent base stations, which is chosen from thescrambling code set of the base station;

As shown in FIG. 3, the fixed delay Td represents time delay betweenstart time of cell identifier signal frame and start time of servicebase station pilot signal frame; fixed delay Td determines the centralposition of the search window; search window width W defines the widthof the search window; the mobile station searches for the cellidentifier signal in the time range (defined by center Td and width W)according to the scrambling code corresponding to the cell identifiersignal issued from the network.

Step 2: The mobile station measures TDOAs of received cell identifiersignal and base station pilot signal with TDOA positioning method andreports the measured data;

Step 3: Determine whether there is a time difference consistent to thefixed delay Td between cell identifier signal frame and base stationpilot signal frame according to the measured data reported from themobile station, i.e., determine whether to use the TOA positioningmethod with the repeater as the reference point to position the mobilestation on the basis that whether there is time delay Td in the TDOAmeasuring result; if there is a time difference that is consistent tofixed delay Td, go to step 4; otherwise go to step 7;

Step 4: Read the calibrated value TOA_(c) of TOA between the repeaterand the base station, and initiate RIT measuring function of the basestation;

The calibrated value TOA_(c) is obtained during the calibration processwith the following method after the repeater is installed: place acommon 3G cell phone at several meters to the repeater, and utilizes RTT(Round Trip Time) measuring function of the base station to measure RTTat the cell phone, TOA_(c) is calculated as: TOA_(c)=(½) RTT; as shownFIG. 4, the calibrated value TOA_(c) between repeater and service basestation is D1 shown in FIG. 1;

Step 5: Convert the measured RTT reported from the base station intomeasured value TOA_(m) of TOA, herein TOA_(m)=(½) RTT, which is the TOAfrom the mobile station to the base station via the repeater, subtractthe calibrated value TOA_(c) of TOA from TOA_(m) and take the result asTOA TOA_(trans) from the mobile station to the repeater, i.e.,TOA_(trans)=TOA_(m)−TOA_(c);, TOA_(trans) is D2 shown in FIG. 4;

Step 6: Use a common TOA algorithm to determine the distance from themobile station to the repeater to accomplish mobile station positioningwork, i.e., calculate the distance from the mobile station to therepeater with calibrated value of TOA from the base station and repeaterand TDOA between the base station and mobile station.

Step 7: If there is no fixed delay Td between cell identifier signalframe and base station pilot signal frame, it indicates the mobilestation is not in the coverage of the repeater; in this case, mobilestation positioning can be carried out with conventional TDOA method orTOA method.

A repeater that supports mobile station positioning, wherein:

The method according to the present invention can be implemented in theconventional protocol framework of 3GPP (Third Generation PartnerProject) with signaling and measuring functions defined in conventionalprotocols.

1. A repeater, wherein a cell identifier generator module is added todownlink circuit structure of said repeater, said cell identifiergenerator module comprising: a synchronization searching unit forsearching for a synchronization signal of a base station, a time delayunit for generating a fixed delay between a frame start time of a cellidentifier signal and a frame start time of a base station pilot signal,and a cell identifier signal generating unit for generating a cellidentifier signal code word; said time delay unit generating the fixeddelay according to the searching result of the synchronization searchingunit.
 2. A repeater according to claim 1, wherein: an input end of saidcell identifier generator module is connected to a low-noise amplifiermodule of the repeater, and an output end of said cell identifiergenerator module is connected to a power amplifier module of therepeater via a coupler.
 3. A repeater according to claim 2, wherein saidcell identifier generator module also comprises: a down-conversion unit,an A/D (Analog to Digital) conversion unit, a D/A (Digital to Analog)conversion unit, a, up-conversion unit, and a filtering unit; whereinsaid down-conversion unit is designed to carry out frequency conversionfrom RF to intermediate frequency for received signals; said A/Dconversion unit is designed to carry out sampling and quantification forintermediate frequency signals; said D/A conversion unit is designed tocarry out D/A conversion to obtain a base-band form of the cellidentifier signal; said up-conversion unit is designed to carry outconversion from base-band to RF for the cell identifier signal; saidfiltering unit is designed to carry out band restriction for the cellidentifier signal to control frequency leakage to adjacent frequency;said cell identifier signal is coupled to an input end of the poweramplifier in the downlink circuit structure of the repeater via said D/Aunit, up-conversion unit, and filtering unit.
 4. A method forpositioning mobile station, comprising: (1) Issuing a cell identifiersignal code word, fixed delay, and search window width for the mobilestation according to a positioning request of the mobile station; (2)The mobile station utilizing a TDOA (Time Difference Of Arrival)measuring function to measure TDOAs of a cell identifier signal and abase station pilot signal and reporting the measured data; (3)Determining whether there is a time difference consistent to a fixeddelay between the cell identifier signal and the base station pilotsignal according to the reported data from the mobile station; if so,going to step (4); otherwise going to step (7); (4) Reading calibratedvalue TOA_(c) of TOA (Time Of Arrival) between a repeater and the basestation, and initiating an RTT (Round Trip Time) measuring function ofthe base station to measure RTT of the mobile station, whereinTOA_(c)=(½) RTT; (5) Converting the measured RTT reported from the basestation into measured value TOA_(m) of TOA, wherein TOA_(m)=(½) RTT,which is the TOA from the mobile station to the base station via therepeater, subtracting the calibrated value TOA_(c) of TOA from therepeater to the base station from TOA_(m) and taking the result as TOATOA_(trans) from the mobile station to the repeater, whereinTOA_(trans)=TOA_(m) −TOA_(c); (6) Calculating distance between themobile station and the repeater through multiplying TOA_(trans) withlight velocity; and (7) Determining position of the mobile station withthe mobile station positioning method.
 5. A method for positioningmobile station according to claim 4, wherein said cell identifier signalis a scrambling code of the base station, which is different from thatof adjacent base stations.
 6. A method for positioning mobile stationaccording to claim 4, wherein said mobile station positioning method instep (7) is TDOA positioning method.
 7. A method for positioning mobilestation according to claim 4, wherein said mobile station positioningmethod in step (7) is TOA positioning method.